In order to harmoniously move the screens of a group of screens, it is known in EP-A-2 120 119 to determine for each screen a shift parameter between two reference positions, of which one is shared by the various screens of the group. It is also known in WO-A-2009/150345 to move the end of a screen when it becomes the farthest away from a shared position to be reached for a group of screens. It is finally known in U.S. Pat. No. 7,599,612 to take the winding diameter and the thickness of a flexible element into account in order to configure a roller blind.
These various approaches aim to obtain, on the same façade, a harmony in the movement of the blinds during their opening and their closing, in particular when the latter have a similar course of travel between a shared high position and a low position and when they are controlled simultaneously.
However, irregularities can occur during the movement of a load bar which can be slowed down or temporarily wedged in a slider. In this case, with the known techniques, this load bar is moved with a delay in relation to the other load bars of a group of screens which are controlled in speed.
These irregularities or braking in the movement of a load bar can be accidental, due to an obstacle, or recurring, for example in the case of increased friction resulting from the ageing of an installation. These irregularities induce load variations on the actuator which drives the winding member of the flexible element and these load variations are not taken into account in controlling the movement of the load bar.
It is moreover known, for example in U.S. Pat. No. 6,283,190, to start a drive motor of a winding tube of a blind string at full power, then to carry out a control in terms of speed. Here again, in the event of a slowdown or blocking, the lag of a load bar cannot be caught up.
It is these disadvantages that the invention intends more particularly to overcome by proposing a new method for controlling a screen comprising a load bar and a flexible element supporting this load bar, with this method making it possible to optimise the movement of the load bar, including in the case of irregularity, for example in the event of friction of the load bar in sliders.